Communications systems that utilize non-stationary users or relay sites frequently use directional antennas to direct radio signals between stations. These directional antennas require a high degree of pointing accuracy to maintain adequate power in the communication link and to minimize interference with neighboring receptors. A means of maintaining this pointing accuracy by correcting for inertial reference drift or target movement is required.
Communications systems are designed to be as efficient as possible, both in terms of spectral efficiency and power efficiency. Moving stations require tracking systems to assist in directing radio signal beams. Tracking systems ensure that beams widths can be kept as narrow as possible. Narrow beam widths reduce the amount of power necessary for effective communication between stations, prevent unwanted parties from potentially receiving signals, and prevent overlap of signals onto spatially adjacent receivers, which is important for regulatory compliance.
Prior art tracking systems generally require large directional antennas and several degrees of separation between satellites to ensure tracking of the desired source. In practice however, antennas are often small aperture antennas and satellite separation can be minimal, creating the possibility of impairment to the tracking signal from those nearby satellites. These impairments change the nature of the tracking signal, corrupting the tracking signal and degrading the accuracy of the tracking capability. This in turn reduces the effective data capacity of data links between stations. In some instances, small aperture antennas use inertial pointing based on inertial reference units instead of tracking systems to point at the desired satellite and to stabilize the antenna orientation. But inertial reference units are susceptible to drift over time and operate without feedback for pointing accuracy. Because of this lack of feedback, mechanical movement accuracy of antennas degrades due to mechanical wear and perturbation from external sources, such as vibration.